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  <div class="section" id="concepts">
<h1>Concepts<a class="headerlink" href="#concepts" title="Permalink to this headline">¶</a></h1>
<div class="section" id="constfunctionobject">
<h2>ConstFunctionObject<a class="headerlink" href="#constfunctionobject" title="Permalink to this headline">¶</a></h2>
<p>Is an object with a <code class="docutils literal"><span class="pre">const</span></code> call operator:</p>
<div class="highlight-cpp"><div class="highlight"><pre><span class="n">concept</span> <span class="n">ConstFunctionObject</span>
<span class="p">{</span>
    <span class="k">template</span><span class="o">&lt;</span><span class="n">class</span><span class="p">...</span> <span class="n">Ts</span><span class="o">&gt;</span>
    <span class="k">auto</span> <span class="k">operator</span><span class="p">()(</span><span class="n">Ts</span><span class="o">&amp;&amp;</span><span class="p">...)</span> <span class="k">const</span><span class="p">;</span>
<span class="p">};</span>
</pre></div>
</div>
<div class="section" id="requirements">
<h3>Requirements:<a class="headerlink" href="#requirements" title="Permalink to this headline">¶</a></h3>
<p>The type <code class="docutils literal"><span class="pre">F</span></code> satisfies <code class="docutils literal"><span class="pre">ConstFunctionObject</span></code> if</p>
<ul class="simple">
<li>The type <code class="docutils literal"><span class="pre">F</span></code> satisfies <code class="docutils literal"><span class="pre">std::is_object</span></code>, and</li>
</ul>
<p>Given</p>
<ul class="simple">
<li><code class="docutils literal"><span class="pre">f</span></code>, an object of type <code class="docutils literal"><span class="pre">const</span> <span class="pre">F</span></code></li>
<li><code class="docutils literal"><span class="pre">args...</span></code>, suitable argument list, which may be empty</li>
</ul>
<table border="1" class="docutils">
<colgroup>
<col width="38%" />
<col width="62%" />
</colgroup>
<thead valign="bottom">
<tr class="row-odd"><th class="head">Expression</th>
<th class="head">Requirements</th>
</tr>
</thead>
<tbody valign="top">
<tr class="row-even"><td><code class="docutils literal"><span class="pre">f(args...)</span></code></td>
<td>performs a function call</td>
</tr>
</tbody>
</table>
</div>
</div>
<div class="section" id="nullaryfunctionobject">
<h2>NullaryFunctionObject<a class="headerlink" href="#nullaryfunctionobject" title="Permalink to this headline">¶</a></h2>
<p>Is an object with a <code class="docutils literal"><span class="pre">const</span></code> call operator that accepts no parameters:</p>
<div class="highlight-cpp"><div class="highlight"><pre><span class="n">concept</span> <span class="n">NullaryFunctionObject</span>
<span class="p">{</span>
    <span class="k">auto</span> <span class="k">operator</span><span class="p">()()</span> <span class="k">const</span><span class="p">;</span>
<span class="p">};</span>
</pre></div>
</div>
<div class="section" id="id1">
<h3>Requirements:<a class="headerlink" href="#id1" title="Permalink to this headline">¶</a></h3>
<ul class="simple">
<li><code class="docutils literal"><span class="pre">ConstFunctionObject</span></code></li>
</ul>
<p>Given</p>
<ul class="simple">
<li><code class="docutils literal"><span class="pre">f</span></code>, an object of type <code class="docutils literal"><span class="pre">const</span> <span class="pre">F</span></code></li>
</ul>
<table border="1" class="docutils">
<colgroup>
<col width="38%" />
<col width="62%" />
</colgroup>
<thead valign="bottom">
<tr class="row-odd"><th class="head">Expression</th>
<th class="head">Requirements</th>
</tr>
</thead>
<tbody valign="top">
<tr class="row-even"><td><code class="docutils literal"><span class="pre">f()</span></code></td>
<td>performs a function call</td>
</tr>
</tbody>
</table>
</div>
</div>
<div class="section" id="unaryfunctionobject">
<h2>UnaryFunctionObject<a class="headerlink" href="#unaryfunctionobject" title="Permalink to this headline">¶</a></h2>
<p>Is an object with a <code class="docutils literal"><span class="pre">const</span></code> call operator that accepts one parameter:</p>
<div class="highlight-cpp"><div class="highlight"><pre><span class="n">concept</span> <span class="n">UnaryFunctionObject</span>
<span class="p">{</span>
    <span class="k">template</span><span class="o">&lt;</span><span class="k">class</span> <span class="nc">T</span><span class="o">&gt;</span>
    <span class="k">auto</span> <span class="k">operator</span><span class="p">()(</span><span class="n">T</span><span class="o">&amp;&amp;</span><span class="p">)</span> <span class="k">const</span><span class="p">;</span>
<span class="p">};</span>
</pre></div>
</div>
<div class="section" id="id2">
<h3>Requirements:<a class="headerlink" href="#id2" title="Permalink to this headline">¶</a></h3>
<ul class="simple">
<li><code class="docutils literal"><span class="pre">ConstFunctionObject</span></code></li>
</ul>
<p>Given</p>
<ul class="simple">
<li><code class="docutils literal"><span class="pre">f</span></code>, an object of type <code class="docutils literal"><span class="pre">const</span> <span class="pre">F</span></code></li>
<li><code class="docutils literal"><span class="pre">arg</span></code>, a single argument</li>
</ul>
<table border="1" class="docutils">
<colgroup>
<col width="38%" />
<col width="62%" />
</colgroup>
<thead valign="bottom">
<tr class="row-odd"><th class="head">Expression</th>
<th class="head">Requirements</th>
</tr>
</thead>
<tbody valign="top">
<tr class="row-even"><td><code class="docutils literal"><span class="pre">f(arg)</span></code></td>
<td>performs a function call</td>
</tr>
</tbody>
</table>
</div>
</div>
<div class="section" id="binaryfunctionobject">
<h2>BinaryFunctionObject<a class="headerlink" href="#binaryfunctionobject" title="Permalink to this headline">¶</a></h2>
<p>Is an object with a <code class="docutils literal"><span class="pre">const</span></code> call operator that accepts two parameter:</p>
<div class="highlight-cpp"><div class="highlight"><pre><span class="n">concept</span> <span class="n">UnaryFunctionObject</span>
<span class="p">{</span>
    <span class="k">template</span><span class="o">&lt;</span><span class="k">class</span> <span class="nc">T</span><span class="p">,</span> <span class="k">class</span> <span class="nc">U</span><span class="o">&gt;</span>
    <span class="k">auto</span> <span class="k">operator</span><span class="p">()(</span><span class="n">T</span><span class="o">&amp;&amp;</span><span class="p">,</span> <span class="n">U</span><span class="o">&amp;&amp;</span><span class="p">)</span> <span class="k">const</span><span class="p">;</span>
<span class="p">};</span>
</pre></div>
</div>
<div class="section" id="id3">
<h3>Requirements:<a class="headerlink" href="#id3" title="Permalink to this headline">¶</a></h3>
<ul class="simple">
<li><code class="docutils literal"><span class="pre">ConstFunctionObject</span></code></li>
</ul>
<p>Given</p>
<ul class="simple">
<li><code class="docutils literal"><span class="pre">f</span></code>, an object of type <code class="docutils literal"><span class="pre">const</span> <span class="pre">F</span></code></li>
<li><code class="docutils literal"><span class="pre">arg1</span></code>, a single argument</li>
<li><code class="docutils literal"><span class="pre">arg2</span></code>, a single argument</li>
</ul>
<table border="1" class="docutils">
<colgroup>
<col width="42%" />
<col width="58%" />
</colgroup>
<thead valign="bottom">
<tr class="row-odd"><th class="head">Expression</th>
<th class="head">Requirements</th>
</tr>
</thead>
<tbody valign="top">
<tr class="row-even"><td><code class="docutils literal"><span class="pre">f(arg1,</span> <span class="pre">arg2)</span></code></td>
<td>performs a function call</td>
</tr>
</tbody>
</table>
</div>
</div>
<div class="section" id="mutablefunctionobject">
<h2>MutableFunctionObject<a class="headerlink" href="#mutablefunctionobject" title="Permalink to this headline">¶</a></h2>
<p>Is an object with a <code class="docutils literal"><span class="pre">mutable</span></code> call operator:</p>
<div class="highlight-cpp"><div class="highlight"><pre><span class="n">concept</span> <span class="n">MutableFunctionObject</span>
<span class="p">{</span>
    <span class="k">template</span><span class="o">&lt;</span><span class="n">class</span><span class="p">...</span> <span class="n">Ts</span><span class="o">&gt;</span>
    <span class="k">auto</span> <span class="k">operator</span><span class="p">()(</span><span class="n">Ts</span><span class="o">&amp;&amp;</span><span class="p">...);</span>
<span class="p">};</span>
</pre></div>
</div>
<div class="section" id="id4">
<h3>Requirements:<a class="headerlink" href="#id4" title="Permalink to this headline">¶</a></h3>
<p>The type <code class="docutils literal"><span class="pre">F</span></code> satisfies <code class="docutils literal"><span class="pre">MutableFunctionObject</span></code> if</p>
<ul class="simple">
<li>The type <code class="docutils literal"><span class="pre">F</span></code> satisfies <code class="docutils literal"><span class="pre">std::is_object</span></code>, and</li>
</ul>
<p>Given</p>
<ul class="simple">
<li><code class="docutils literal"><span class="pre">f</span></code>, an object of type <code class="docutils literal"><span class="pre">F</span></code></li>
<li><code class="docutils literal"><span class="pre">args...</span></code>, suitable argument list, which may be empty</li>
</ul>
<table border="1" class="docutils">
<colgroup>
<col width="38%" />
<col width="62%" />
</colgroup>
<thead valign="bottom">
<tr class="row-odd"><th class="head">Expression</th>
<th class="head">Requirements</th>
</tr>
</thead>
<tbody valign="top">
<tr class="row-even"><td><code class="docutils literal"><span class="pre">f(args...)</span></code></td>
<td>performs a function call</td>
</tr>
</tbody>
</table>
</div>
</div>
<div class="section" id="evaluatablefunctionobject">
<h2>EvaluatableFunctionObject<a class="headerlink" href="#evaluatablefunctionobject" title="Permalink to this headline">¶</a></h2>
<p>Is an object that is either a <code class="docutils literal"><span class="pre">NullaryFunctionObject</span></code>, or it is an <code class="docutils literal"><span class="pre">UnaryFuntionObject</span></code> that accepts the <code class="docutils literal"><span class="pre">identity</span></code> function as a parameter.</p>
<div class="section" id="id5">
<h3>Requirements:<a class="headerlink" href="#id5" title="Permalink to this headline">¶</a></h3>
<ul class="simple">
<li><code class="docutils literal"><span class="pre">NullaryFunctionObject</span></code></li>
</ul>
<p>Given</p>
<ul class="simple">
<li><code class="docutils literal"><span class="pre">f</span></code>, an object of type <code class="docutils literal"><span class="pre">const</span> <span class="pre">F</span></code></li>
</ul>
<table border="1" class="docutils">
<colgroup>
<col width="38%" />
<col width="62%" />
</colgroup>
<thead valign="bottom">
<tr class="row-odd"><th class="head">Expression</th>
<th class="head">Requirements</th>
</tr>
</thead>
<tbody valign="top">
<tr class="row-even"><td><code class="docutils literal"><span class="pre">f()</span></code></td>
<td>performs a function call</td>
</tr>
</tbody>
</table>
<p>Or:</p>
<ul class="simple">
<li><code class="docutils literal"><span class="pre">UnaryFuntionObject</span></code></li>
</ul>
<p>Given</p>
<ul class="simple">
<li><code class="docutils literal"><span class="pre">f</span></code>, an object of type <code class="docutils literal"><span class="pre">const</span> <span class="pre">F</span></code></li>
<li><code class="docutils literal"><span class="pre">identity</span></code>, which is the identity function</li>
</ul>
<table border="1" class="docutils">
<colgroup>
<col width="40%" />
<col width="60%" />
</colgroup>
<thead valign="bottom">
<tr class="row-odd"><th class="head">Expression</th>
<th class="head">Requirements</th>
</tr>
</thead>
<tbody valign="top">
<tr class="row-even"><td><code class="docutils literal"><span class="pre">f(identity)</span></code></td>
<td>performs a function call</td>
</tr>
</tbody>
</table>
</div>
</div>
<div class="section" id="invocable">
<h2>Invocable<a class="headerlink" href="#invocable" title="Permalink to this headline">¶</a></h2>
<p>Is an object for which the <code class="docutils literal"><span class="pre">INVOKE</span></code> operation can be applied.</p>
<div class="section" id="id6">
<h3>Requirements:<a class="headerlink" href="#id6" title="Permalink to this headline">¶</a></h3>
<p>The type <code class="docutils literal"><span class="pre">T</span></code> satisfies <code class="docutils literal"><span class="pre">Invocable</span></code> if</p>
<p>Given</p>
<ul class="simple">
<li><code class="docutils literal"><span class="pre">f</span></code>, an object of type <code class="docutils literal"><span class="pre">T</span></code></li>
<li><code class="docutils literal"><span class="pre">Args...</span></code>, suitable list of argument types</li>
</ul>
<p>The following expressions must be valid:</p>
<table border="1" class="docutils">
<colgroup>
<col width="42%" />
<col width="58%" />
</colgroup>
<thead valign="bottom">
<tr class="row-odd"><th class="head">Expression</th>
<th class="head">Requirements</th>
</tr>
</thead>
<tbody valign="top">
<tr class="row-even"><td><code class="docutils literal"><span class="pre">INVOKE(f,</span> <span class="pre">std::declval&lt;Args&gt;()...)</span></code></td>
<td>the expression is well-formed in unevaluated context</td>
</tr>
</tbody>
</table>
<p>where <code class="docutils literal"><span class="pre">INVOKE(f,</span> <span class="pre">x,</span> <span class="pre">xs...)</span></code> is defined as follows:</p>
<ul class="simple">
<li>if <code class="docutils literal"><span class="pre">f</span></code> is a pointer to member function of class <code class="docutils literal"><span class="pre">U</span></code>:<ul>
<li>If <code class="docutils literal"><span class="pre">std::is_base_of&lt;U,</span> <span class="pre">std::decay_t&lt;decltype(x)&gt;&gt;()</span></code> is true, then <code class="docutils literal"><span class="pre">INVOKE(f,</span> <span class="pre">x,</span> <span class="pre">xs...)</span></code> is equivalent to <code class="docutils literal"><span class="pre">(x.*f)(xs...)</span></code></li>
<li>otherwise, if <code class="docutils literal"><span class="pre">std::decay_t&lt;decltype(x)&gt;</span></code> is a specialization of <code class="docutils literal"><span class="pre">std::reference_wrapper</span></code>, then <code class="docutils literal"><span class="pre">INVOKE(f,</span> <span class="pre">x,</span> <span class="pre">xs...)</span></code> is equivalent to <code class="docutils literal"><span class="pre">(x.get().*f)(xs...)</span></code></li>
<li>otherwise, if x does not satisfy the previous items, then <code class="docutils literal"><span class="pre">INVOKE(f,</span> <span class="pre">x,</span> <span class="pre">xs...)</span></code> is equivalent to <code class="docutils literal"><span class="pre">((*x).*f)(xs...)</span></code>.</li>
</ul>
</li>
<li>otherwise, if <code class="docutils literal"><span class="pre">f</span></code> is a pointer to data member of class <code class="docutils literal"><span class="pre">U</span></code>:<ul>
<li>If <code class="docutils literal"><span class="pre">std::is_base_of&lt;U,</span> <span class="pre">std::decay_t&lt;decltype(x)&gt;&gt;()</span></code> is true, then <code class="docutils literal"><span class="pre">INVOKE(f,</span> <span class="pre">x)</span></code> is equivalent to <code class="docutils literal"><span class="pre">x.*f</span></code></li>
<li>otherwise, if <code class="docutils literal"><span class="pre">std::decay_t&lt;decltype(x)&gt;</span></code> is a specialization of <code class="docutils literal"><span class="pre">std::reference_wrapper</span></code>, then <code class="docutils literal"><span class="pre">INVOKE(f,</span> <span class="pre">x)</span></code> is equivalent to <code class="docutils literal"><span class="pre">x.get().*f</span></code></li>
<li>otherwise, if <code class="docutils literal"><span class="pre">x</span></code> does not satisfy the previous items, then <code class="docutils literal"><span class="pre">INVOKE(f,</span> <span class="pre">x)</span></code> is equivalent to <code class="docutils literal"><span class="pre">(*x).*f</span></code></li>
</ul>
</li>
<li>otherwise, <code class="docutils literal"><span class="pre">INVOKE(f,</span> <span class="pre">x,</span> <span class="pre">xs...)</span></code> is equivalent to <code class="docutils literal"><span class="pre">f(x,</span> <span class="pre">xs...)</span></code></li>
</ul>
</div>
</div>
<div class="section" id="constinvocable">
<h2>ConstInvocable<a class="headerlink" href="#constinvocable" title="Permalink to this headline">¶</a></h2>
<p>Is an object for which the <code class="docutils literal"><span class="pre">INVOKE</span></code> operation can be applied.</p>
<div class="section" id="id7">
<h3>Requirements:<a class="headerlink" href="#id7" title="Permalink to this headline">¶</a></h3>
<p>The type <code class="docutils literal"><span class="pre">T</span></code> satisfies <code class="docutils literal"><span class="pre">ConstInvocable</span></code> if</p>
<p>Given</p>
<ul class="simple">
<li><code class="docutils literal"><span class="pre">f</span></code>, an object of type <code class="docutils literal"><span class="pre">const</span> <span class="pre">T</span></code></li>
<li><code class="docutils literal"><span class="pre">Args...</span></code>, suitable list of argument types</li>
</ul>
<p>The following expressions must be valid:</p>
<table border="1" class="docutils">
<colgroup>
<col width="42%" />
<col width="58%" />
</colgroup>
<thead valign="bottom">
<tr class="row-odd"><th class="head">Expression</th>
<th class="head">Requirements</th>
</tr>
</thead>
<tbody valign="top">
<tr class="row-even"><td><code class="docutils literal"><span class="pre">INVOKE(f,</span> <span class="pre">std::declval&lt;Args&gt;()...)</span></code></td>
<td>the expression is well-formed in unevaluated context</td>
</tr>
</tbody>
</table>
<p>where <code class="docutils literal"><span class="pre">INVOKE(f,</span> <span class="pre">x,</span> <span class="pre">xs...)</span></code> is defined as follows:</p>
<ul class="simple">
<li>if <code class="docutils literal"><span class="pre">f</span></code> is a pointer to member function of class <code class="docutils literal"><span class="pre">U</span></code>:<ul>
<li>If <code class="docutils literal"><span class="pre">std::is_base_of&lt;U,</span> <span class="pre">std::decay_t&lt;decltype(x)&gt;&gt;()</span></code> is true, then <code class="docutils literal"><span class="pre">INVOKE(f,</span> <span class="pre">x,</span> <span class="pre">xs...)</span></code> is equivalent to <code class="docutils literal"><span class="pre">(x.*f)(xs...)</span></code></li>
<li>otherwise, if <code class="docutils literal"><span class="pre">std::decay_t&lt;decltype(x)&gt;</span></code> is a specialization of <code class="docutils literal"><span class="pre">std::reference_wrapper</span></code>, then <code class="docutils literal"><span class="pre">INVOKE(f,</span> <span class="pre">x,</span> <span class="pre">xs...)</span></code> is equivalent to <code class="docutils literal"><span class="pre">(x.get().*f)(xs...)</span></code></li>
<li>otherwise, if x does not satisfy the previous items, then <code class="docutils literal"><span class="pre">INVOKE(f,</span> <span class="pre">x,</span> <span class="pre">xs...)</span></code> is equivalent to <code class="docutils literal"><span class="pre">((*x).*f)(xs...)</span></code>.</li>
</ul>
</li>
<li>otherwise, if <code class="docutils literal"><span class="pre">f</span></code> is a pointer to data member of class <code class="docutils literal"><span class="pre">U</span></code>:<ul>
<li>If <code class="docutils literal"><span class="pre">std::is_base_of&lt;U,</span> <span class="pre">std::decay_t&lt;decltype(x)&gt;&gt;()</span></code> is true, then <code class="docutils literal"><span class="pre">INVOKE(f,</span> <span class="pre">x)</span></code> is equivalent to <code class="docutils literal"><span class="pre">x.*f</span></code></li>
<li>otherwise, if <code class="docutils literal"><span class="pre">std::decay_t&lt;decltype(x)&gt;</span></code> is a specialization of <code class="docutils literal"><span class="pre">std::reference_wrapper</span></code>, then <code class="docutils literal"><span class="pre">INVOKE(f,</span> <span class="pre">x)</span></code> is equivalent to <code class="docutils literal"><span class="pre">x.get().*f</span></code></li>
<li>otherwise, if <code class="docutils literal"><span class="pre">x</span></code> does not satisfy the previous items, then <code class="docutils literal"><span class="pre">INVOKE(f,</span> <span class="pre">x)</span></code> is equivalent to <code class="docutils literal"><span class="pre">(*x).*f</span></code></li>
</ul>
</li>
<li>otherwise, <code class="docutils literal"><span class="pre">INVOKE(f,</span> <span class="pre">x,</span> <span class="pre">xs...)</span></code> is equivalent to <code class="docutils literal"><span class="pre">f(x,</span> <span class="pre">xs...)</span></code></li>
</ul>
</div>
</div>
<div class="section" id="unaryinvocable">
<h2>UnaryInvocable<a class="headerlink" href="#unaryinvocable" title="Permalink to this headline">¶</a></h2>
<p>Is an object for which the <code class="docutils literal"><span class="pre">INVOKE</span></code> operation can be applied with one parameter.</p>
<div class="section" id="id8">
<h3>Requirements:<a class="headerlink" href="#id8" title="Permalink to this headline">¶</a></h3>
<ul class="simple">
<li><code class="docutils literal"><span class="pre">ConstInvocable</span></code></li>
</ul>
<p>Given</p>
<ul class="simple">
<li><code class="docutils literal"><span class="pre">f</span></code>, an object of type <code class="docutils literal"><span class="pre">const</span> <span class="pre">F</span></code></li>
<li><code class="docutils literal"><span class="pre">arg</span></code>, a single argument</li>
</ul>
<table border="1" class="docutils">
<colgroup>
<col width="42%" />
<col width="58%" />
</colgroup>
<thead valign="bottom">
<tr class="row-odd"><th class="head">Expression</th>
<th class="head">Requirements</th>
</tr>
</thead>
<tbody valign="top">
<tr class="row-even"><td><code class="docutils literal"><span class="pre">INVOKE(f,</span> <span class="pre">arg)</span></code></td>
<td>the expression is well-formed in unevaluated context</td>
</tr>
</tbody>
</table>
</div>
</div>
<div class="section" id="binaryinvocable">
<h2>BinaryInvocable<a class="headerlink" href="#binaryinvocable" title="Permalink to this headline">¶</a></h2>
<p>Is an object for which the <code class="docutils literal"><span class="pre">INVOKE</span></code> operation can be applied with two parameters.</p>
<div class="section" id="id9">
<h3>Requirements:<a class="headerlink" href="#id9" title="Permalink to this headline">¶</a></h3>
<ul class="simple">
<li><code class="docutils literal"><span class="pre">ConstInvocable</span></code></li>
</ul>
<p>Given</p>
<ul class="simple">
<li><code class="docutils literal"><span class="pre">f</span></code>, an object of type <code class="docutils literal"><span class="pre">const</span> <span class="pre">F</span></code></li>
<li><code class="docutils literal"><span class="pre">arg1</span></code>, a single argument</li>
<li><code class="docutils literal"><span class="pre">arg2</span></code>, a single argument</li>
</ul>
<table border="1" class="docutils">
<colgroup>
<col width="42%" />
<col width="58%" />
</colgroup>
<thead valign="bottom">
<tr class="row-odd"><th class="head">Expression</th>
<th class="head">Requirements</th>
</tr>
</thead>
<tbody valign="top">
<tr class="row-even"><td><code class="docutils literal"><span class="pre">INVOKE(f,</span> <span class="pre">arg1,</span> <span class="pre">arg2)</span></code></td>
<td>the expression is well-formed in unevaluated context</td>
</tr>
</tbody>
</table>
</div>
</div>
<div class="section" id="metafunction">
<h2>Metafunction<a class="headerlink" href="#metafunction" title="Permalink to this headline">¶</a></h2>
<p>Given</p>
<ul class="simple">
<li><code class="docutils literal"><span class="pre">f</span></code>, a type or a template</li>
<li><code class="docutils literal"><span class="pre">args...</span></code>, any suitable type, which may be empty</li>
</ul>
<table border="1" class="docutils">
<colgroup>
<col width="37%" />
<col width="63%" />
</colgroup>
<thead valign="bottom">
<tr class="row-odd"><th class="head">Expression</th>
<th class="head">Requirements</th>
</tr>
</thead>
<tbody valign="top">
<tr class="row-even"><td><code class="docutils literal"><span class="pre">f::type</span></code></td>
<td>The type is the result of the metafunction</td>
</tr>
<tr class="row-odd"><td><code class="docutils literal"><span class="pre">f&lt;args...&gt;::type</span></code></td>
<td>The type is the result of the metafunction</td>
</tr>
</tbody>
</table>
</div>
<div class="section" id="metafunctionclass">
<h2>MetafunctionClass<a class="headerlink" href="#metafunctionclass" title="Permalink to this headline">¶</a></h2>
<p>Given</p>
<ul class="simple">
<li><code class="docutils literal"><span class="pre">f</span></code>, a type or a template</li>
<li><code class="docutils literal"><span class="pre">args...</span></code>, any suitable type, which may be empty</li>
</ul>
<table border="1" class="docutils">
<colgroup>
<col width="40%" />
<col width="60%" />
</colgroup>
<thead valign="bottom">
<tr class="row-odd"><th class="head">Expression</th>
<th class="head">Requirements</th>
</tr>
</thead>
<tbody valign="top">
<tr class="row-even"><td><code class="docutils literal"><span class="pre">f::apply::type</span></code></td>
<td>The type is the result of the metafunction</td>
</tr>
<tr class="row-odd"><td><code class="docutils literal"><span class="pre">f::apply&lt;args...&gt;::type</span></code></td>
<td>The type is the result of the metafunction</td>
</tr>
</tbody>
</table>
</div>
</div>


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